how to activate object on collision

i have 8 cube objects

object 0 is called lap 0 object 1 is called lap 1 object 2 is called lap 2 object 3 is called lap 3 object 4 is called lap 4 object 5 is called lap 5 object 6 is called activate cube object 7 is called ramp cube

the game is a racing game were you destroy the cars.

i want object 0-5 (all the lap cubes) activated when collided with. on object 6 and 7 i want it to be visible when object 5 is collided with the player.